Electrical apparatus



May 24, 1927. 1,629,866 1.. o. GRONDAHL ET AL ELECTRI CAL APPARATUS Original Filed Nov. 3, 1923 rays.

INVENTORS. L .0. Granola/1 UNITED STATES LABS o. eEonnAnL, or rrrrsnunen, AND. HARRY m. RYDER, or Emnronn, mun- BYLVANIA, nssrenoas TO THE UNION swr'rcn a SIGNAL courmv, or swrss- VALE, rENNsYLvnmn, a coaroaarxon 0E PENKSYLVANIA.

. ELEc'rnIcn'L nrranaros.

Original application filed flovember a, was, Serial ab.- svam. Divided and anapplication m November 10, 1826.

Our invention relates to electrical apparatus, and particularly to apparatus for translating alternating current of a comparativel low frequency into alternating current of comparatively high frequency, and for supplying two such currents o'fdifferent high frequencies to a single device.

Apparatus embod ing our invention is Efrticularly adapte I for use in supplying h frequency alternating currents to the rails of a railway in railway trafiic controlp both halves of secondary 6 of transformer systems. v

he present application is 'a-division of our 'co-p'ending application filed Nov. 3, 1923, Serial No. 672,642, for electrical apparatus.

We will describe three formsand arrangements 'of apparatus embodying our invention, and will then point out the novel features thereof in claim.

In the accompanying drawing, Fig. 1 is a diagrammatic viewshowing one form of electrical apparatus embodying our invention. Figs. 2 and 3 are views showing modifications of the apparatus illustrated inFig. 1 and also embodying our invention. 7

Similar reference characters refer to similar parts ineach of the three views.

Referring first to Fig. 1 the a Earatus comprises two, electron tubes A and each havin a grid 3, a filament 4, and a late 5. The laments .4 of the tubesA an B are connected in parallel across the terminals of secondary 6 of a power transformer E. The primary 7 of this transformer is constantly "supplied with alternating current of some convenient low frequency such as cycles per second. The rid 3 of tube A is connected by means 0% wire 35, rid condenser 8, coil 10, and wire 11 with t e midoint a of secondary 6 of transformer E. high resistance grid leak 9 is connected around the grid condenser 8 in accordance with the usual practice. The grid circuit of tube A may be tuned to resonance at any desired frequency by means of a variable condenser 13 in multiple with coil 10. .Tube 13 is provided with a grid circuitj including a grid condenser 8, a grid leakffi, aj'coil 10, and 'a variable condenser 13, similar in all respects to the corresponding parts asso- 'ciated with tube A. a g t Electromotive force" is supplied to the Serial N0. 147,528.

nating current from some suitable source not shownin the drawing. The late circuit for tube A passes from the eft hand terminal of secondary 22 of transformer G through impedance 23, wire 21, primar 17 ofoutput transformer H, wire 15, coi 14 in inductive relation with coil 10, wire 16, late 5 and filament 4 of tube A, through E in parallel, to mid-point a, and wire 12 to mid-point b of secondary 22 of transformer G. 'In a similar manner the plate c rcuit for tube B may' be traced from the right hand terminal of secondary 22 of transformer (I, through impedance 23, wire '20,'primary wind1ng 18 of out at transformer H, wire 15, coil 14" in in uctive relation with coil 10', w ir"e"16, plate 5 and filament 4 of tube B, through both halves of secondary 6 of transformer E in parallel to mid-point a, and wire 12 back to mid-point b of secondary 22 of transformer G. The

secondary winding 19 of out 'ut transformer H is constantly connected with the device to which it is desired to supply high frequency currents. As shown in the drawing this device comprises therails l and 1 of a section C-D of railway track.

It will be seen fromthe fore ing that each of the tubes-A and B functions as an oscillator in the usual and well known manner. Current flows, however, in the plate circuit of'each tube only when the plate of that tube is positive with respect to the associated filament. At any instant however,

the ,-rel ative polarities of the, voltages .applied to the plates of the two posite, and it therefore follows that during one half-cycle of each wave of the electromotive force supplied by transformer G, plate current flows through tube A, and durmg the other half-cycle plate current flows through tube B. The grid circuits of the two tubes A and B are tuned to resonance at different frequencies, so that the high frequency currents superimposed upon the plate circuits of these two tubes have difierent periodicities. During the halfcycle in whichtube A is supplying high frequency tubes are op-- current to winding 17, no high frequency current is flowing in winding 18 of transformer H. During the half-cycle in which tube B is supplyin high frequency currents to winding 18, no igh frequency current s flowing in winding 17. Secondary 19, is,

however, in inductive relation with both windings l7 and 18 and as a result a. composite current is supplied to the ra1ls 1 and 1. This current consists of a seriesof groups of impulses, the lengths of all such groups being equal, each alternate group consisting of impulses of one high frequency, and the intervening groups consisting of 1mpulses of a different high frequency. For all ordinary purposes the effect is the same as if two se arate alternating currents of these two di fierent frequencies were being continuouslysugplied at the same time to the section C- A condenser 24 'is shown across each half of secondary 22 of transformer G and lts associated inductance 23, the purpose of this condenser being to prevent the passage of high frequency currents from the plate circuits upon which they are superimposed, back into transformer G.

Under some conditions of operation It may be desirable to supply to section C D larger amounts of power than can continually be supplied by single electron tubes of commercial sizes. Under such conditions the output of tubes A and B may be amphfied as illustrated in Fig. 2 before being supplied to primaries 17 and 18 of output transformer H. In Fig. 2 the circuits for the filaments and grids of oscillator tubes A and B are the same as in Fig. 1. The plate circuit for tube A however, now passes from the left hand terminal of secondary 22 of transformer G, through inductance 23, wire 36, primary winding 28 of transformer S, wire 37, cell 14 in inductive relation with coil 10, wire 38, plate 5 and filament 4 of tube A, through both halves of secondary 6 of transformer E in parallel to mid-point a and wire 12, back to mid-point b of secondary 22 of transformer G. In a similar manner primary 26 of transformer T is included in the plate circuit for tube B. High frequency energy is created in the plate circuit of tubes A and B is am lified by electron tube amplifiers M an N, respectively. The filaments 4 of these tubes are connected in parallel across'the terminals of secondary 6 of transformer E.

Referring particularly to amplifier M, the grid circuit for this tube passes from one terminal of secondary 29 of transformer S, through wire 39, grid 3 and filament 4 of amplifier M, through both halves of secondary 6 of transformer E in parallel, and wires 12 and 40, back to secondary 29 of transformer S. It will thus be during each alternate half-cycle o the eleclain that the high frequency current superimposed upon the plate circuit of tube A will cause a corresponding high frequency electromotive force'to be applied to the grid 3 of tube M. The plate circuit of this tube passes from the left hand terminal of seconda 22 of transformer G, through inductance 23, wires 36 and 41, winding 17 of output transformer H, wire 42, plate 5 and filament 4 of tube M, through bothhalves of secondary (l of transformer E in parallel and wire 12 back to mid-point b of secondary 22 of transformer G. The circuits for tube N are similar to those just described in connection with tube M, it being clear from the draw ing that high frequency current su erimposed upon the plate circuit of tube presses a corresponding high frequency electromotive force upon the grid 3 of tube N,

thus creating corresponding high frequency current in the plate circuit of this tube and hence in winding 18 of output transformer H. It follows therefore that section C--D tubes M and N of Fig. 2. The plate circuit for tube A passes from the left hand terminal of secondary 22 of transformer G, through inductance 23, wire 43, primar winding 32 of transformer K, wire 44, coil 14 in inductive relation with coil 10, wire 45, plate 5 and filament 4 of tube, A, both halves "of secondary 6 of transformer E in parallel, and wire 12 back to mid-point b of secondary 22 of transformer G. In similar manner the plate circuit for tube B includes a second primary winding 33 of transformed vK. The grid circuit for tube P passes from one terminal of secondary 34 of transformer K, through wire 46, grid 3 and filament 4 of tube P, through both halves of secondary 6 of transformer E in parallel and wires 12 and 47 back to secmay be traced from the left hand side of secondary 22 of transformer G through inductance 23, Wires 43 and 48, winding 31 of transformer L, plate 5 and filament 4 of tube P, through both halves of secondary 6 of transformer E in parallel, and wire 12, back to mid-point b of secondary '22 of transformer G. Windin L is constantly connect 30 of transformer across the rails of section CD and the current supplied to this section under these conditions has the same characteristics as with the apparatus shown in Figs. 1 and 2.

Although we have herein shown and described only three forms of electrical apparatus embodying our invention, it is understood that various changes and modifications may be made therein within the scope 10 of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim is:

In combination, a stretch of railway track, and means for at times supplying the rails of the stretch with alternate impulses of alternating currents of different frequencies.

In testimony whereof We aifix our signatures.

LARS O. GRONDAHL. HARRY M. RYDER. 

